Step 17: Bond, Solar Cell Bond

Step 18: Testint, testing, 1,2,3

You're done building! Now, its time to test. Measure the voltage of the pair of AAA NiMH batteries you will be using, then insert them into the batter...

Have you ever wanted a waterproof, weatherproof, lightweight portable solar charger for small electronics? Whether you're a backpacker, a survivalist, or just trying to preserve the planet so you can enjoy it outdoors a little longer, this is the project for you.

About a month ago I was on an 8 day backpacking trip through Shenandoah National Park. I'd arranged to have a friend meet me for re-supply halfway through. Unfortunately, I'd fallen in with a fast crowd and was 27 miles past where we'd arranged to meet. Fortunately, I was carrying my cell phone, which typically has about a week of standby time. Unfortunately, away from civilization the signal is much weaker, so unbeknownst to me I only had about a day and a half of standby in this case. I found this out on day three. I began thinking about backpackable solar charging solutions. I did manage to yogi a cell phone and get ahold of her, but in a less busy park things might have gotten really out of hand.

I'd had fantastic weather until day six, when I got hit with real backpacking weather: thunderstorms and cold, driving rain. When I got home, my digi-cam had water damage. It mostly works, but sometimes won't turn on or turn off now, and the LCD has cloudy water spots, this despite being inside a ziplock bag inside my pack. I began thinking about lightweight waterproof electronics enclosures.

Then, I started thinking "Hey, I can do both at the same time!" Nine prototypes later, this is what I had, the "Rain or Shine Solar Charger." In addition to being useful for backpacking, this charger attaches with parachute buckles, so you could attach it to a messenger bag, or a bookbag, or hang it in your kitchen window. It takes about ten hours to charge a typical cell phone, but it's a storage charger, so you could leave the charger in the sun to collect energy during the day, then plug the cell hone in at night to charge from the stored energy.

This is a fairly complicated project, which will likely stretch either your sewing skills or your electronics skills, but the results are well worth it.

This is ideal for campers or travelers. I bought a high capacity solar charger and I was surprised how long it stores energy. The concept of a waterproof solar charger is new to me, do they convert less solar energy due to the protection from water? Thx. for this thoughtful post!

how much did this cost? I'm on a budget. and would you have to actually make the bag? I have mad sewing skills, but I would think that a seal line brand map bag would work well and maybe be more waterproof. how waterproof is it really? I'm a sea kayaking guide and this would be pretty awesome to charge on the deck of my boat. I run out of battery on my phone by the end of a 5 day trek.

love the ible you did great i have a question would it not just be easier to use the solar pack to charge some AA batteries and buy a little cell phone charger from walmart they run on 2 AA bateries and then just charge 2 AA batteries and put them in the them in the portable cell phone charger and bing bang boom done then just put it all away in your pouch when your done and yay your not lost in the wilderness

I'm building one of these as a project for school, and one thing I noticed is that the AnyVolt Micro output cuts out when the input is dropped below 2.2V, which, if I'm not mistaken, means that you could work the whole setup down to a Schottky diode and the AnyVolt Micro as it would automatically cut off the batteries from outputting if they drop below 2.2V. I ahven't finished testing the AVM yet so I'm not 100% sure of this yet though.

One issue is the quiescent draw of the AnyVolt Micro - it'll run the battery down in dim light just staying on. The other thing the comparator circuit does for you is provides for burst charging - my cell phone turns the backlight on when it starts charging, which draws significant power. By storing up the energy then charging at a higher rate, then turning off to recharge the batteries, the amount of total power consumed by the phone's backlight is reduced. The comparator adds hysteresis, which is important with those limitations. Incedentally, since I wrote this Dimension came out with another regulator called LVBoost which is smaller, higher current, and can run down to .7v input, plus has significantly lower quiescent draw. You can get more juice out of the battery that way - like you say, the AVM cuts out at 2.2v, which works, but it only uses about half the capacity of the battery before cutting out to recharge. If I was doing this application today that's what I'd use.

Gotcha, I'd neglected the quiescent draw. I don't have the issue of the backlight coming on with my phone, but I added a USB port for my MP3 player, which does turn the screen on when it charges (I'm tempted to reconnect it's hold switch to the backlight to save power). Oh wow that would be sweet, although I think my instructor might get mad as we just spent a bunch of money ordering AVM's haha. I'll keep that in mind if I do a v2.0 though.

I have a newbie question. Most of the diy solar projects I've seen you have to make sure that regulators diodes etc. are used and that you cut off one end of a phone charger and solder everything together. Instead of cutting off the wires from a charger, couldn't you just hook the solar cells directly to the charger? I figured that the charger has all of the necessary electronics already. I'm new to soldering and electronics so forgive my lack of knowledge.

You can snip the wires off a car cigarette adapter and then connect the cigarette adapter to your solar panels, and then use that to charge your phone. You are right. The adapter that normally connects to the car battery has regulators and diodes and all of that stuff included. It takes a 12 volt charge from the battery and converts it to 5volts so you can safely charge your phone.

Although, its probably a good idea to install a diode between the solar panels and the cigarette adapter because I have seen instances where cheap cell phone battery chargers still drain the battery of the cell phone even when they are plugged into a cigarette adapter when the car isn't running. Diodes are super cheap and easy to install, so it shouldn't be too difficult. The regulator IS the cigarette adapter that changes the voltage to a normal level for your cell phone.

The black box or end of the connector contains the transformer, diodes, and anything else that would prevent you from overcharging or damaging your battery pack.

"The last nice thing about this system is that in an absolute emergency, say, after an alien invasion has blotted out the sun, you could replace the rechargeable NiMH batteries with disposable alkalines and charge your cell phone from them. In most circumstances you'd never need this capability, but if you have to contact the president regarding the aliens' one weakness, it might just save the planet.

lolThanx for the instruction i had in plans to make a exactly similar last summer but now it will be finished'

has anyone got a plan/design to use the small panels from solar garden lights to make a larger panel that could charge a 12V battery? I got about 30 lights that I want to caniblaize the panels out of and make something larger. thanks.

It is doable, you could probably follow the instructions from makezine, their actual magazine had an article in it on using salvaged solar panels. If you want to get any significant source of charge though, you will need a large and efficient panel. I went to Canadian Tire and bought an 80 dollar solar panel which outputs 12 volts @ 400ma in direct sunlight. It works great, but to charge a 7ah battery, it takes like 2 days. Those little panels *might* squeak 400ma.

What I did was plug the panel into one of those car booster packs, let it charge all day, go to work... whatever. Then when I got home, I would run my laptop off of the charged booster pack through an inverter. (stay off my case about the waste of time going from DC-AC-DC, i know, this was an experiment) It worked great! The only thing i didn't do was charge the laptop off of the booster pack or run it at full CPU. These two things would kill the booster pack very fast! The booster pack usually died almost fully, I could have extended this charge by bypassing the extra step (DC-AC-DC). I was up north working and this was a little experiment I did to stop myself from going nuts with boredom... (no soldering for 2 MONTHS!)

Nice idea. I wonder how to mod this project so that i can supply energy to a microcontroller. Then, I would be able to make some nice projects to put at sunlight with no need for external power. (but, then... I guess the batteries and the electronic components should not be exposed to direct sunlight)

This is definitely a cool project! I'm not very tech savvy so this question might seem a little weird... but I'm assuming I can use the same concept to make one to plug in small kitchen appliances, etc.? Would I need to change anything about the design other than the bag? (don't think it is neccesary to put a toaster in a bag LOL). And a kinda off the subject question... does anyone know where I can find an instructable on making my own enclosed compost tumbler out of recyclables?

Hi, Sounds great! How would you go about making one large enough (powerful enough) to run the new portable Microwaves to take aboard a boat? Or to run a small fan or toaster for fancier camping? Or to run a computer and a lamp during a power outage? Seriously, you have a great idea.

Hi, Well, the basic idea would be the same, but a microwave is serious power, at least a couple hundred watts. This project is running at most a solar charge power of .45W and 1.5W to the cell phone. That would be a scale-up of 100 times or more in terms of power. This would necessitate different components and construction techniques. Also, this project only turns the charger on when the battery is ready, which might be any time between "now" and "an hour from now" depending on the sun and the state of charge of the battery. That's necessary for cell phone charging, but a bit annoying when you want breakfast. With a larger system you'd need a much larger solar panel, of course. Something rated to charge a 12V battery would be ideal. You'd need bigger batteries, a 12v lead acid deep cycle battery would be the usual route. Really the application is different enough that it'd be a new instructable.

What a great idea to use an intermediate storage battery so you can save the solar energy! How much does this device weigh? Have you hiked with it? If so, how well does it work? Approximately how much did it cost for parts? I love your idea too. It looks like a great project for anybody who has a cell phone and likes to get off the beaten path for a few hours or a few days. Plus, it could be an essential piece of backpacking equipment for a life-saving emergency. Thank you for taking time to make such an awesome instructable!